RIO DE JANEIRO – Police investigating the death of former boxing champion Arturo Gatti are working on the assumption his wife strangled him with her purse strap while he drunkenly slept. The woman's lawyer, however, insists she is innocent and was too "fragile" to kill a boxer.

Lead investigator Moises Teixeira told The Associated Press on Monday nothing is being ruled out but he is certain the woman acted by herself.

"It was technically impossible for a third person to have been in the flat," where Gatti was found dead early Saturday, Teixeira said. "The investigation isn't finished, but we continue to think she did this alone."

Gatti's 23-year-old Brazilian wife, Amanda Rodrigues, told investigators she awoke Saturday about 6 a.m. to find her husband's body in the apartment they rented in Porto de Galinhas, a seaside resort in northeastern Pernambuco state.

Rodrigues told police she had a fight with Gatti after dinner Friday night and he pushed her to the ground, resulting in minor injuries to her elbow and chin. Witnesses also reported to police the couple fought and that Gatti was drunk.

Rodrigues told police the 37-year-old former junior welterweight champion then got into a cab with their son and returned to their rented apartment, leaving her alone downtown.

Teixeira said witnesses told police Gatti left his son to sleep in the apartment, then returned to the city center to find his wife. She arrived at the apartment before he did and waited for him. They then both went upstairs together.

Rodrigues told police she slept on the second floor of the apartment with her son, while Gatti slept on the first floor. She told police she awoke at 6 a.m. to feed her son and discovered her husband's body. Police say he most likely had been killed at least four hours before that.

Teixeira said police do not think anyone else entered the apartment and killed Gatti — he said there were no signs of forced entry and electronic locks indicated nobody else had entered the room aside from Rodrigues and Gatti.

The investigator said Rodrigues told them she thought her husband had committed suicide or that someone had entered the apartment and killed him. Teixeira ruled out both scenarios.

Rodrigues' sister, Flavia, told the newspaper Folha de S. Paulo there is "no way she could have strangled a man of that size."

Rodrigues' attorney, Celio Avelino, told the AP he agreed with Flavia's conclusion and he would request Amanda be freed from jail Tuesday pending the conclusion of the investigation.

"She is fragile, young and skinny — how could she kill a boxing champion?" Avelino said. "When she awoke, she presumed he had committed suicide. But she had nothing to do with it."

Flavia Rodrigues said her sister told her she thought Gatti had committed suicide — though she said he knew of no reason the boxer would kill himself or why the pair fought the night before his death.

"Sure, they had fights," Flavia said. "But he was crazy about her."

The sister told Recife's TV Jornal news station that "Amanda told us she didn't kill Arturo, and we believe her."

"My sister, like us, is very religious and would be incapable of killing anyone," Flavia said. "She found him already dead. It's up to the police to discover what happened in the flat."

The pair married in 2007 and according to Rodrigues had a rocky relationship. Authorities were told the couple was extremely jealous of each other and that Gatti constantly complained about her clothing when she traveled to Brazil, police spokeswoman Milena Saraiva said.

According to Brazilian law, police accuse a person of a crime but it is up to the prosecutor to formally file a charge. Teixeira said police have until July 22 to deliver their findings to the prosecutor's office, but he hoped the investigation would be completed before then.

Rodrigues was accused of the crime Sunday and taken into police custody. She has been transferred to a woman's prison in the state capital Recife. She maintains her innocence.

Gatti, Rodrigues and their 10-month-old son arrived in Brazil on Friday for what they told a local real estate agent was a second honeymoon. The baby, who was unhurt, is now with Rodrigues' family in Brazil.

Gatti, a Canadian, fought an epic trilogy with Micky Ward that branded him one of the most exciting fighters of his generation. HBO said Monday it will re-air the three fights Friday and Saturday.

Gatti retired in 2007 with a career record of 40-9 and 31 knockouts. Known for his straightforward punching and granitelike chin, Gatti captured the super featherweight title in 1995, when he defeated Tracy Harris Patterson in Atlantic City, N.J. He won the junior welterweight title in 2004.

At a news conference Monday announcing a super middleweight tournament at Madison Square Garden, there was a moment of silence in his honor.

"I had the opportunity to represent Arturo when I worked for Main Events," promoter Gary Shaw told The Associated Press. "If there's anybody with a great personality and was a special type of person, it was Arturo Gatti."